The United States says it is speeding up weapons deliveries to the Saudi-led coalition battling Houthi fighters in Yemen.
U.S. Deputy Secretary of State Antony Blinken said Americans also "have established a joint coordination planning cell in the Saudi operation center,” as part of the effort to oust the Houthis, Shi’ite militants backed by neighboring Iran.
"Saudi Arabia is sending a strong message to the Houthis and their allies that they cannot overrun Yemen by force,'' Blinken told reporters in the Saudi capital Riyadh, according to the Reuters news agency.
"As part of that effort, we have expedited weapons deliveries, we have increased our intelligence sharing" and set up the planning cell, he said.
Pentagon spokesman Colonel Steve Warren confirmed Tuesday the U.S. is looking to deliver munitions to its allies involved in the Yemen air campaign.
"It's a combination of pre-existing orders made by our partner nations and some new requirements as they expend munitions," Warren said.
On Tuesday, Saudi-led coalition jets bombed a military installation in southern Yemen as local tribes battled with forces loyal to the Shi'ite rebels in the area, forcing them out and seizing their makeshift camp and weapons, military officials said.
But militants with al-Qaida in the Arabian Peninsula reportedly took control of a border crossing in Yemen's Hadramawt province on Tuesday.
The U.S. was "very closely" watching such reports, Warren said. The U.S. is "always concerned by AQAP's activities," he added, but "we have the capability to conduct unilateral CT [counterterrorism] operations" in Yemen.
UNICEF cites civilian toll
The fighting in southern Ibb province came as UNICEF, the United Nations children's agency, said the conflict has displaced about 100,000 people in Yemen, increasing pressure on hospitals and other services.
The conflict in Yemen has displaced 100,000 people, UNICEF says.
Saying such internal displacement endangers children's health and interrupts their education, UNICEF has called for special attention and protection for children and their families, in line with international humanitarian law.
The agency said at least 74 children have been killed and 44 wounded since March 26, when the air campaign began.
A medical volunteer in Ibb's Maytam district said the airstrike on a Republican Guards camp wounded at least 25 military men. The rebel television station, al-Masirah, reported three children also were killed in a school near the camp. The volunteer, who asked to remain anonymous out of fear of reprisal, could not verify the deaths.
The military unit supports Ali Abdullah Saleh, the former president allied with the Shi'ite rebels in their bid to grab power in Yemen. His successor is the Western-backed president, Abd-Rabbu Mansour Hadi, who on March 25 fled Yemen's provisional capital, the port city of Aden, for refuge in Saudi Arabia.
The Saudi coalition so far has been unable to stop the rebels' advance.
About 50 kilometers (30 miles) south of the military camp, local tribes battled with rebel fighters who had set up a makeshift camp in the area, driving the rebels away and seizing their weapons, said a local resident said, who also asked not to be identified for security reasons.
Civilians have suffered amid the violence that mushroomed from an internal power struggle into a regional war drawing in neighboring Saudi Arabia and its allies.
A Saudi soldier loads ammunition from a position at Saudi Arabia's border with Yemen, April 6, 2015.
According to the World Health Organization, more than 540 people have been killed and 1,700 wounded in the fighting in Yemen over the past three weeks.
Children have been especially vulnerable, said Julien Harneis, UNICEF's Yemen representative.
"They are being killed, maimed and forced to flee their homes, their health threatened and their education interrupted," Harneis said in a statement released Monday in Amman, Jordan. Warring factions also have increased recruitment of troops under age 18.
Red Cross aid arriving
The International Committee of the Red Cross said Tuesday its first flight transporting medical personnel to Yemen has reached the capital, Sana'a.
Dominik Stillhart, a senior Red Cross official, noted the arrival in a Twitter post and said tons of urgently needed medical supplies will arrive by air and sea once transportation is cleared.
The Red Cross said Monday that, while it had received the Saudi-led coalition's approval, logistical concerns about flying into the war-torn country were delaying the process.
Humanitarian groups say they are running out of supplies. They have called for a temporary halt to the fighting so medical teams and fresh medical supplies can arrive in the country and residents can identify and bury their dead.
UNICEF said the violence has disrupted water supplies in areas of southern Yemen and sewage is overflowing in some locations, raising the risk of disease outbreak. Water systems have been repeatedly damaged in Aden and two other areas, UNICEF said, adding it's providing fuel for water pumps.
Pitched battle for Aden
On Monday, rebels and their allies made their strongest push yet to seize control of Aden, a main stronghold of Hadi's supporters. Intense clashes left many bodies in the streets.
The fighting raised doubts over the possibility of landing ground forces from the Saudi-led coalition to carve out a secure enclave for Hadi, who fled the country two weeks ago.
"Conditions are very dangerous right now," UNICEF's Gamila Hibatullah in Aden was quoted as saying. "Hospitals are overflowing, and even ambulances have been hijacked."
'China is deeply worried'
On Tuesday, China's Foreign Ministry added its support to calls for a cease-fire in Yemen, after Russia and the Red Cross appealed for a military pause to allow humanitarian aid deliveries and the evacuation of civilians last week.
"China is deeply worried" and seeks a cease-fire to "avoid further civilian casualties," spokeswoman Hua Chunying said at a daily news briefing in Beijing.
"China also hopes that all relevant sides can earnestly implement relevant U.N. Security Council resolutions and Gulf Cooperation Council proposals and resolve the crisis through political dialog so as to quickly restore Yemen's stability and normal legal order,” Hua said.
China, a low-key diplomatic player in the Middle East despite its reliance on oil from the region, previously had called for a political solution.
Jeff Seldin contributed to this report from the Pentagon. Some additional material came from Reuters and AP.